Napkin-Ring Sign on Coronary CT Angiography for the Prediction of Acute Coronary Syndrome

Abstract

The aim of this study was to determine the predictive value of the napkin-ring sign on coronary computed tomography angiography (CTA) for future acute coronary syndrome (ACS) events in patients with coronary artery disease. Recent studies have reported a close association between the napkin-ring sign on coronary CTA and thin-cap fibroatheroma. The subjects of this prospective study were 895 consecutive patients who underwent coronary CTA examination and were followed for >1 year. The primary endpoint was an ACS event (cardiac death, nonfatal myocardial infarction, or unstable angina pectoris). The coronary CTA analysis included the presence of obstructive plaque, positive remodeling (PR), low-attenuation plaque (LAP), and the napkin-ring sign. The napkin-ring sign was defined by the following criteria: 1) the presence of a ring of high attenuation around certain coronary artery plaques; and 2) attenuation of the ring presenting higher than those of the adjacent plaque and no >130 Hounsfield units. Of the 12,727 segments, 1,174 plaques were observed, including plaques with PR in 130 segments (1.0%), LAP in 107 segments (0.8%), and napkin-ring signs in 45 segments (0.4%). Thirty-six of the 45 plaques with napkin-ring signs (80%) overlapped with those showing either PR or LAP. During the follow-up period (2.3 ± 0.8 years), 24 patients (2.6%) experienced ACS events, and plaques developed in 41% with a napkin-ring sign. Segment-based Cox proportional hazards models analysis showed that PR (p < 0.001), LAP (p = 0.007), and the napkin-ring sign (p < 0.0001) were independent predictive factors for future ACS events. Kaplan-Meier analysis demonstrated that plaques with napkin-ring signs showed a higher risk of ACS events compared with those without a napkin-ring sign. The present study demonstrated for the first time that the napkin-ring sign demonstrated on coronary CTA was strongly associated with future ACS events, independent of other high-risk coronary CTA features. Detection of the napkin-ring sign could help identify coronary artery disease patients at high risk of future ACS events.